Berry fool - Marjakiisseli (about 3€)

5 dl berry juice2 ½ tbsp potato flour (perunajauhot)2-3 dl berries(sugar)
1. Blend the juice and the potato flour together in a saucepan.2. Heat the mixture until boiling. Stir the mixture throughout the heating.3. Put the berries on a serving dish and pour the mixture on top of them.4. Check the taste and add some sugar if needed.